Air starter for gas turbine



Aug. 9, 1955 L.. R. woslKA AIR STARTER FOR GAS TURBINE Filed Oct. 25, 1948 ATTORNIEY United States Patent Ain STARTER non GAS TURBINE Leon R. Wosika, San Diego, Calif., assignor to Solar Aircraft Company, San Diego, Calif., a corporation of California Application October 25, 1948, Serial No. 56,320

7 Claims. (Cl. 6039.14)

This invention relates to starters for gas turbines, and particularly to starters employing compressed air as the power medium.

An object of the invention is to provide a starter for a gas turbine that is inexpensive, simple, and light.

Another object is to provide an air starter for a gas turbine that is exceptionally economical in the use of compressed air.

Another object is to provide an air starter for a gas turbine that is substantially foolproof and is immune to disorder during long periods of disuse.

Other more specific objects and features of the invention will appear from the description to follow.

Gas turbines of a well known type employ a rotating shaft which is` driven by the rotor of the turbine and which in turn drives the rotor of a compressor that supplies compressed air to a combustion chamber where it is mixed with fuel and burned to provide a greatly increased volume of gas for driving the gas turbine. Since in such devices the compressor must be operating before proper combustion can take place, some starting means for bringing the shaft up to speed is required. Various types of starters have been employed. Some are mechanically connected to the turbine shaft, and may consist of an electric motor, an auxiliary gas motor, etc. It has also been proposed to supply compressed air to the gas turbine through the same channel that the products of combustion are normally supplied to it, which channel includes an annular passage containing stator vanes which direct the gas against the rotor vane. The objection to such an arrangement is that it requires a very large volume of compressed air, a volume so large that it is often impractical to supply it.

The present invention enables economical use of compressed air for starting, by providing a special nozzle through which the starting air is introduced. This noz zle, in the preferred form of the invention, is formed within one of the stator vanes of the turbine. Since the special air nozzle is designed solely for the starting operation, it can be dimensioned to pass a relatively small volume of air at relatively high pressure. Thus, two pounds per second of air at 300 p. s. i. is adequate to start a 400 H. P. gas turbine within seconds. Because of the small air consumption, it is feasible to supply it from a high pressure air bottle through a reducing valve. A relatively small bottle capable of containing air at 3000 p. s. i. is capable of providing several starts for such an engine without recharging.

Referring now to the drawing:

Fig. 1 is a side elevation of a typical gas turbine equipped with a starter in accordance with the invention;

Fig. 2 is a cross section taken in the plane li-Il of Fig. l;

Fig. 3 is a sectional view taken in the plane III-III of Fig. 2;

Fig. 4 is a sectional view taken in the plane IV-IV of Fig. 2; and

2,714,802 Patented Aug. 9, 1955 Fig. 5 is a sectional view taken in the plane V-V of Fig. 3.

Referring to Fig. l there is shown a typical gas turbine consisting of a coaxially mounted turbine and compressor 11, each having a rotor mounted on a common shaft 13. The construction of the compressor constitutes no part of the present invention, and it will suf. tice to say that air enters the right end of the compressor 11 as indicated by the arrow 14 and is compressed and delivered into a scroll 15 which conducts it to the inlet end of a combustion chamber 16, the output of which constitutes the working gas, which is delivered through a manifold in the form of a scroll 17 to the gas turbine 10.

Referring now to Figs. 2 and 3, the gas turbine comprises a rotor 18 carrying a plurality of rotor vanes 19, and a stator 20 carrying a plurality of stator vanes 21 which direct the working gas at the proper angle against the rotor vanes 19. The scroll 1'7 delivers the working gas to the front ends of the stator vanes 21, imparting a rotation to the gases which facilitates their entry between the stator vanes. However, this feature is standard construction in turbines and does not constitute a part of the present invention. After the working gas has passed through the rotor vanes 19 it is discharged through a tailpipe 23 (Fig. l).

In accordance with the present invention, there is substituted for one of the stator vanes 21, a special hollow stator vane 2S which functions as a nozzle to direct an auxiliary gas, such as air, against the rotor vanes 19 for starting. As shown in Fig. 3, this special hollow vane or nozzle` 25 is slightly larger than the conventional stator vanes 21, but additional space is provided for it so that all of the passages 2o through which the working gas passes are of the same size.

Air may be supplied to the nozzle 25 through a pipe 27 from any suitable source. ln Fig. l the source is shown as an air bottle 28 which is connected through a solenoid valve 29 and a pressure-reducing valve 300 to the pipe 27. For the purpose of charging it, the bottle 28 may be connected through a check valve 310 to an air supply pipe 320.

It is usually most desirable, from the standpoint of efficiency when the starting nozzle is out of operation to employ only one nozzle 2S. However in some instances where more torque is required, or where it is desired to employ a larger volume of air at a lower pressure, a larger number of the nozzles 25 may be provided.

As shown in Figs. 2 to 5 inclusive, the nozzle 25 is an integral unit having an entrance passage 3l) extending substantially radially with respect to the turbine axis and a discharge passage 31 emerging from the side of the entrance passage 30. The discharge passage 31 is rectangular in cross sectional shape and expands in cross section from the passage 30 to the discharge orifice. Preferably, the discharge orice has an eliective area which substantially bridges the entrance ends of a plurality of passages between the rotor vanes 19, as seen in Figure 3. This expanding passage 31 permits the use of starting air at such high pressures that the velocity of the air at its point of impingernent on the turbine blades may be supersonic. Without the passagiie of expanding cross section, the shock expansion would result in poor nozzle efficiency and therefore a larger volume of air would be necessary to obtain the same starting power. This in turn necessitates a large supply tank or bottle 28.

The nozzle 25 is supported in place by being extended through apertures provided therefor in the annular inner and outer bands 32 and 33 respectively which support the regular stator vanes 21 and cooperate with the latter to define the stator passages 26. The nozzle 25 is shown welded to the inner band 32 at 34, and to the outer band scribed, obvious modifications will occur to a personl skilled in the art, and I do not desire to be limited t0 the exact details illustrated. However, wherever the term` stator vane is used in the claims it is'to be understood that the term means a vane shaped and arranged to direct the working gas or fluid against the rotor vanesy in the manner customary in the tunrbine art and as exemplied in Figure 3 of the drawing.

I claim:

1. In a gas turbine comprising a rotor having an annular series of rotor vanes and gas manifold means including a stator having an annular series of stator vanes adjacent said rotor vanes for directing a working gas issuing from said manifold against said rotor vanes: means for directing an auxiliary gas against said rotor vanes to start said turbine comprising a single nozzle vane in said stator disposed between a pair of adjacent working gas passages and having an outlet passage the discharge area of which is substantially equal to that of one of said working gas passages and arranged to direct an issuing auxiliary gaseous discharge against said rotor vanes in the same direction as the gas issuing from said working gas passages deiined by said stator vanes whereby the full force of said auxiliary gaseous discharge is effective for driving said rotor, and means for supplying an auxiliary gas to said single nozzle vane at predetermined time only to etect starting of said turbine.

2. Apparatus according to claim 1 in which said nozzle vane is formed exteriorly to also serve as one of said stator vanes.

3. Apparatus according to claim 2 in which said nozzle vane defines a discharge passage of rectangular cross i section expanding in cross sectional area in the direction of ilow through the discharge passage.

4. Apparatus according to claim 1 in which said nozzle vane comprises an inlet passage of generally cylindrical shape extending substantially radially inwardly toward the axis of the turbine and communicating at its side with said outlet passage.

5. Apparatus according to claim l, wherein said nozzle passage has an eiective discharge orifice area substantially bridging the entrance ends of a plurality of passages between the rotor vanes.

6. In a gas turbine, a rotor having an annular series of rotor vanes, a stator having an annular series of stator vanes adjacent to said rotor vanes, means for supplying a working gas to the passages between said stator vanes for direction thereby against the rotor vanes, at least one of said stator vanes having an entrance side in the form of a radially directed tubular inlet, a discharge side in the form of a diagonally directed axially opening discharge passage, and a connecting passage between said inlet and said discharge passage, a source of auxiliary starting gas, and coupling means directly connecting said source with said tubular inlet.

7. Apparatus according to claim 6, whereinv said connecting passage progressively increases to an eifective area at said discharge orifice which substantially bridges the entrance ends of a plurality of passages between the rotor vanes.

References Cited in the file of this patent UNITED STATES PATENTS 1,289,960 Taylor Dec. 31, 1918 1,442,876 Hartman Jan. 23, 1923 2,242,767 Traupel May 20, 1941 2,411,552 New Nov. 26, 1946 2,457,833 Redding Jan. 4, 1949 FOREIGN PATENTS 7,375 Great Britain July 14, 1910 292,085 Great Britain July 12, 1928 

